The present invention relates to a vehicle light, in particular a taillight of a motor vehicle.
The focus of the ever fast-paced technological developments in the field of motor vehicle lighting systems is to provide additional flexibility to design departments of automobile manufacturers following new technical approaches. The aim is to provide vehicle lights, which are in sync with the design of the motor vehicle, or even form a distinctive feature thereof, while complying with statutory regulations and taking into account general economic and structural conditions.
Apart from having to meet design specifications of defined installation sizes and shapes, vehicle lights are also required to have a harmonious appearance taking into account statutory provisions regarding light functions and light distribution. However, it is difficult to bring about an agreement between function, structure and optical design in the case of taillights, in particular, where the least possible installation depth is additionally required in order to integrate the lights into the flat tailgate or rear region of the vehicle body.
Taillights known from the prior art use rod-shaped fiber-optic light guides, such as those described in DE 100 29 542 A1 by way of example, in which the required light is coupled into the ends of the fiber-optic light guide preferably by way of LEDs (light-emitting diodes). The largest portion of the coupled-in light is radiated outward perpendicular to the longitudinal direction of the fiber-optic light guide via a transparent light exit surface located opposite to a reflective surface. The reflective surface enables the creation of a radiation pattern, i.e., a defined light distribution such as the most uniform possible radiation over a defined surface, for example. This is achieved, for example, using a plurality of prism elements on the reflective surface. The prism elements can also, in operative interaction with an appropriately shaped light exit surface, additionally take on the function of a rear reflector (so-called retro reflector), which reflects the light striking on the vehicle light from the outside.
The disadvantage of this lighting technology known from the prior art is that although it does enable the provision of a vehicle light having relatively less installation depth as is required in the vehicle rear end, in particular, the prism structure is distinctly visible from the clear cover of the light. This prism structure can sometimes have a disturbing or particularly inhomogeneous effect on the visual impression of the light. Due to its transparency (on the light exit surface) and lower installation depth, the fiber-optic light guide additionally appears to be unfavorably two-dimensional in daylight and night designs, that is to say, in the off-state when the fiber-optic light guide is not illuminated and on-state when it is illuminated.
Furthermore, for example, DE 199 50 700 A1, DE 44 25 401 A1 and DE 103 43 639 A1 disclose vehicle lights, which operate using transmitted light technology and in which optical surface elements, such as lens units, prismatic panes or color screens, which are trans-illuminated by a light bulb and/or LED from behind via a reflector, are disposed at least in certain sections between a light source and a front window for achieving a defined light distribution or coloring.
The disadvantageous effect of this arrangement is that the lens units, prismatic panes or color screens and the reflectors have a rather asymmetrical effect on the overall impression of the light since they serve for creating a specified radiation pattern and are designed accordingly. In doing so, the optical design is sidelined, at best. Furthermore, the transmitted light technology using complex reflectors in combination with light bulbs and/or LEDs as light sources requires a relatively large installation space. These lights are therefore unsuitable for use as taillights in the flat tailgate or rear regions of the vehicle body.
It is the object of the present invention to provide a vehicle light, which has a homogeneous appearance while complying with statutory provisions regarding light distribution.
This object is achieved by a vehicle light having a light source and a fiber-optic light guide, into which the light of the light source is coupled on a coupling surface. Means are provided for expanding the aperture angle of an incident light beam, and for deflecting incident light, which means are disposed behind a rear side of the fiber-optic light guide. Preferred developments of the invention are described herein.
The invention is thus based on the idea of integrating expanding and deflecting devices into a vehicle light based on fiber-optic light guides in order to achieve a diffusely and homogeneously illuminating body, which can relatively efficiently meet the requirements regarding light distribution prescribed by law.
For this purpose, the vehicle light preferably includes at least one light source such as a light-emitting diode, and at least one fiber-optic light guide, which has a parallelepiped or rectangular cross-section and into which the light of the light source is coupled, particularly on at least one coupling surface.
Moreover, measures for expanding the aperture angle are provided particularly for scattering or reflecting, in a partly diffuse manner, a light beam or light reflex incident on the expanding devices. The means for expanding the aperture angle preferably cause the increased diffusion of the light striking on them and/or the attenuation of its preferred orientation.
Furthermore, deflecting devices are provided particularly for the directed reflecting of a light beam incident on the deflecting device, which are mounted on or integrated into a reflector device disposed behind a rear side of the fiber-optic light guide or are mounted on the rear side of the fiber-optic light guide or integrated into the fiber-optic light guide. The different deflectors each bring about a deflection of incident light or an incident light beam or a significant portion thereof.
The means for expanding the aperture angle of incident light cause the light guided in the fiber-optic light guide to become partly diffuse and to be coupled out of the fiber-optic light guide in a partly diffuse manner. The desired high-quality and homogeneous appearance of the fiber-optic light guide can thus be achieved for many viewing directions. However, laborious experiments have shown that such a fiber-optic light guide including only means for expanding the aperture angle of incident light is very inefficient, particularly when it comes to meeting statutory provisions regarding the overall radiated light distribution. It has also been observed that a simple reflector such as a reflective layer disposed behind the fiber-optic light guide does not sufficiently increase the efficiency of the latter.
The invention is based on the finding that light, which is expanded by expanders, guided in the fiber-optic light guide and coupled out is only partly diffuse. Due to the means for expanding the aperture angle of an incident light beam, the aperture angle of the light beam does indeed become larger, but it has or retains a defined preferred orientation. It has also been observed that light exits from the front and rear sides of the fiber-optic light guide at different coupling-out points and in different preferred orientations. The centroid direction or the average direction of the light beam directions that are weighted by the respective light intensity or the principal direction or direction of a light beam having maximum light intensity can be used as the preferred orientation of a light beam by way of example.
The present invention utilizes this finding by arranging the deflectors behind the rear side of the fiber-optic light guide to deflect the light coupled out of the rear side of the same in a directed fashion and depending on the different preferred orientations of the coupled-out light so that a relatively large portion of the light coupled out of the rear side of the fiber-optic light guide again enters into the fiber-optic light guide and exits from the front side of the fiber-optic light guide in defined preferred orientations. The defined preferred orientations can be selected depending on the statutory provisions regarding light distribution or light intensity distribution and taking into account the different preferred orientations of the light, which is already coupled out of the front side of the fiber-optic light guide without experiencing any deflection by the deflecting means.
The present invention thus increases the efficiency of a partly diffusely illuminating vehicle light taking into account statutory provisions regarding light distribution or light intensity distribution by the directed deflection of light, which is partly diffusely coupled out of the rear side of the fiber-optic light guide, taking into account and utilizing its different preferred orientations in such a way that this light, after being transmitted through the fiber-optic light guide, contributes significantly toward complying with statutory provisions regarding light distribution or light intensity distribution. In particular, the light, which is deflected by the deflectors and which finally exits from the front side of the fiber-optic light guide in different preferred orientations supplements the light, which is already coupled out of the front side of the fiber-optic light guide in different preferred orientations, in such a way that statutory provisions regarding light distribution or light intensity distribution can be complied with in an energy-efficient manner. For this purpose, the light coupled out of the rear side of the fiber-optic light guide can be deflected in a directed fashion and depending on the coupling-out points with the aid of suitable deflectors, which are adapted to the coupling-out points and/or the corresponding preferred orientation, so that light is substantially radiated in an identical overall preferred orientation out of the front side of the fiber-optic light guide at different points, particularly continuously on a predetermined radiating surface.
Partly diffuse light (light having a relatively large aperture angle, but one preferred orientation) is preferably coupled out of the front and rear sides of the fiber-optic light guide by expanding the light beam in the fiber-optic light guide. The light coupled out of the rear side is deflected with the aid of deflecting mechanisms that are separate from the fiber-optic light guide, and this light finally exits from the front side of the fiber-optic light guide together with the light coupled directly out of the front side of the fiber-optic light guide. The deflecting mechanisms are advantageously formed to enable the deflection of different light beams in such a way, taking into account the different preferred orientations of the light coupled out of the rear side of the fiber-optic light guide, that the different light beams finally after entry into the fiber-optic light guide and exit from the front side of the same together with the light beams coupled directly out of the front side of the fiber-optic light guide have a substantially identical overall preferred orientation at different coupling-points.
Aesthetically speaking, the radiation of partly diffuse light beams thus helps achieve a fiber-optic light guide, which illuminates sufficiently diffusely and efficiently complies with statutory provisions regarding light distribution due to the directed influence on the different preferred orientations of different partly diffuse light beams.
In principle, the invention also includes a vehicle light comprising deflectors that are integrated into the fiber-optic light guide and, for example, have a prism structure formed according to the invention. But its disadvantage is that the prism structure is visible through the rear side of the fiber-optic light guide particularly in the off-state of the vehicle light or the fiber-optic light guide. This visibility is also undesirable in a vehicle light for aesthetic reasons. Therefore, the deflector or the reflector device is preferably formed separately from the fiber-optic light guide or the deflector or the reflector device is not an integral part of the fiber-optic light guide. In particular, the deflectors have no direct contact with the fiber-optic light guide. As a result, the vehicle light, or the fiber-optic light guide in particular, has a homogeneous appearance in the on- and off-states. Particularly when the vehicle light is switched off, this homogeneous appearance is not affected significantly by the transparent contours of the deflector. Due to the arrangement of the deflector behind the fiber-optic light guide or separately from the fiber-optic light guide, the deflector only deflects the coupled-out light and does not influence the light guided in the fiber-optic light guide. This arrangement also has efficiency advantages since, although a deflection of light by the deflector may involve the absorption of light, the external deflector does not absorb the light guided in the fiber-optic light guide.
The invention naturally also includes vehicle lights including a fiber-optic light guide, which radiates light not only from its front side but also from other surfaces, particularly its upper and lower sides. The fiber-optic light guide thus resembles a glowing three-dimensional body or a light cube. Several such light cubes can also be used next to each other in a vehicle light. In particular, the contour of the front side of the fiber-optic light guide and the three-dimensional shape of the fiber-optic light guide, which can be a straight or “curved” rectangular parallelepiped, for example, can be selected relatively freely in terms of design.
The device for deflecting the light particularly preferably includes a facet structure, particularly a facet structure disposed on a reflector device, or a facet structure integrated into a reflector device, a facetted mirror, a stepped mirror or a stepped reflector.
Devices for expanding the light are preferably implemented with the aid of scattering elements (volume scattering elements) integrated into the fiber-optic light guide and/or provision of a rough texture to at least one surface of the fiber-optic light guide. When using volume scattering elements, the expansion of the aperture angle (“subjecting the light to diffusion”) is based on volume effects, whereas the expansion of the aperture angle by means of roughness, or partly diffuse reflection in particular, is based on surface effects. Particularly in the case of deflectors provided outside the fiber-optic light guide, the expanders are preferably an integral part of the fiber-optic light guide. At least the front, upper, lower and/or rear sides of the fiber-optic light guide are preferably roughened up or grained in order to expand the aperture angle of the light beams striking on them and thus subject to diffusion the light guided in the fiber-optic light guide (with total reflection) and the light finally coupled-out.
The expanders are advantageously formed in such a way that light, or the partly diffuse light beams each having a preferred orientation, is coupled out of the front side of the fiber-optic light guide at different front-coupling-out points in different preferred orientations and light, or partly diffuse light beams each having a preferred orientation, is coupled out of the rear side of the fiber-optic light guide at different rear-coupling-out points in different preferred orientations. The devices for expanding the aperture angle thus also cause that light to be partly coupled out of the fiber-optic light guide that would have largely been guided in the fiber-optic light guide based on the total reflection without devices for expanding the aperture angle. The different coupling-out points are illustrated by way of example for different sections of the coupling-out front or rear sides of the fiber-optic light guide. The coupled-out light can constantly or discontinuously, continuously or discretely, change its intensity, or luminance, in particular, or its preferred orientation along the coupling-out surface (front or rear sides) without taking into account the influence of the deflectors.
In one design version of the invention, the fiber-optic light guide can be almost non-transparent in its off-state with the aid of the expanding device. Objects disposed behind the fiber-optic light guide such as deflecting or mounting devices can then be provided with less design effort. This enables the provision of an easily and cost-effectively producible light of high-quality design.
The deflectors are advantageously formed in such a way behind the rear side of the fiber-optic light guide that light deflected by the deflector again enters from the rear side of the fiber-optic light guide and exits from the front side of the same at different exit points in different preferred orientations (the terms “couple-in” and “couple-out” are not used in this connection within the scope of the invention). That is to say, the deflected light is transmitted through the fiber-optic light guide. The light coupled-out of the rear side can thus also be used for complying with statutory provisions regarding light distribution and can contribute toward creating a homogeneous appearance of the vehicle light.
The deflectors and/or expanders are preferably formed in such a way that all the light, which exits from the front side of the fiber-optic light guide (and is deflected by the deflectors), and/or the coupled-out light brings about a specified light distribution or light intensity distribution, particularly by virtue of the fact that the light, which exits from the front side of the fiber-optic light guide (and is deflected by the deflectors), and/or coupled-out light substantially has the same overall preferred orientation at different points or at all points of a predetermined radiating surface.
The deflectors and/or expanders are preferably formed in such a way that light that is deflected by the deflector and that exits from the front side at different exit points together with the light coupled out of the front side at different front-coupling-out points brings about a specified light distribution or light intensity distribution and/or substantially has an identical overall preferred orientation at different exit points or front-coupling-out points. In the case of a vehicle taillight, in particular, the deflecting and expanding devices are formed in such a way that the overall preferred orientation is located parallel to the longitudinal axis of the vehicle since the specified light distribution or light intensity distribution to be complied with frequently prescribes the maximum light intensity for this orientation.
In order to ensure not only a substantially uniform overall preferred orientation of the coupled-out light within a predetermined radiating surface, which can also be part of an overall radiating surface, but also uniform luminance, it is suggested to form the deflectors in such a way that the deflectors located closer to the light source bring about a less efficient deflection of incident light than deflectors located farther from the light source. Alternatively or additionally thereto, the expanding and thus coupling-out means are formed in such a way that the expanders located closer to the light source bring about a less efficient coupling-out of the incident light than expanders located farther from the light source. For example, the concentration or dimensions of the volume scattering elements located closer to the light source can be smaller or the degree of roughness of surfaces located closer to the light source can be lesser or the rough surfaces located closer to the light source can be smaller.
A vehicle taillight is particularly practical if it additionally includes a transparent cover. While the expanders homogenize the appearance of the light for different viewing directions, the three-dimensional fiber-optic light guides disposed behind the transparent cover then give the impression of spatial depth.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.